#704 Tiny performance improvement + code clean-up

(cherry picked from commit 61424f3)

imageio/imageio-webp/src/main/java/com/twelvemonkeys/imageio/plugins/webp/LSBBitReader.java

@@ -35,6 +35,8 @@
 import java.io.EOFException;
 import java.io.IOException;
 
+import static com.twelvemonkeys.lang.Validate.notNull;
+
 /**
  * LSBBitReader
  *
@@ -45,18 +47,17 @@ public final class LSBBitReader {
     // TODO: Consider creating an ImageInputStream wrapper with the WebP implementation of readBit(s)?
 
     private final ImageInputStream imageInput;
-    private int bitOffset = 64;
-    private long streamPosition = -1;
+    int bitOffset = 64;
+    long streamPosition = -1;
 
     /**
-     * Pre buffers up to the next 8 Bytes in input.
+     * Pre-buffers up to the next 8 Bytes in input.
      * Contains valid bits in bits 63 to {@code bitOffset} (inclusive).
-     * Should always be refilled to have at least 56 valid bits (if possible)
      */
     private long buffer;
 
     public LSBBitReader(ImageInputStream imageInput) {
-        this.imageInput = imageInput;
+        this.imageInput = notNull(imageInput);
     }
 
     /**
@@ -89,42 +90,40 @@ public long peekBits(int bits) throws IOException {
         if (bits > 56) {
             throw new IllegalArgumentException("Tried peeking over 56");
         }
+
         return readBits(bits, true);
     }
 
-    //Driver
     private long readBits(int bits, boolean peek) throws IOException {
         if (bits <= 56) {
-
-            /*
-                Could eliminate if we never read from the underlying InputStream outside this class after the object is
-                 created
-            */
-            long inputStreamPosition = imageInput.getStreamPosition();
-            if (streamPosition != inputStreamPosition) {
-                //Need to reset buffer as stream was read in the meantime
+            // Could eliminate if we never read from the underlying InputStream
+            // outside this class after the object is created
+            if (streamPosition != imageInput.getStreamPosition()) {
+                // Need to reset buffer as stream was read in the meantime
                 resetBuffer();
             }
 
             long ret = (buffer >>> bitOffset) & ((1L << bits) - 1);
 
             if (!peek) {
                 bitOffset += bits;
-                refillBuffer();
+
+                if (bitOffset >= 8) {
+                    refillBuffer();
+                }
             }
 
             return ret;
         }
         else {
-            //FIXME Untested
+            // Peek always false in this case
             long lower = readBits(56);
             return (readBits(bits - 56) << (56)) | lower;
         }
     }
 
     private void refillBuffer() throws IOException {
-
-        //Set to stream position consistent with buffered bytes
+        // Set to stream position consistent with buffered bytes
         imageInput.seek(streamPosition + 8);
         for (; bitOffset >= 8; bitOffset -= 8) {
             try {
@@ -138,33 +137,32 @@ private void refillBuffer() throws IOException {
                 return;
             }
         }
-        /*
-            Reset to guarantee stream position consistent with returned bytes
-            Would not need to do this seeking around when the underlying ImageInputStream is never read from outside
-            this class after the object is created.
-        */
+
+        // Reset to guarantee stream position consistent with returned bytes
+        // Would not need to do this seeking around when the underlying ImageInputStream is never read from outside
+        // this class after the object is created.
         imageInput.seek(streamPosition);
     }
 
     private void resetBuffer() throws IOException {
-
         long inputStreamPosition = imageInput.getStreamPosition();
+
         try {
             buffer = imageInput.readLong();
             bitOffset = 0;
             streamPosition = inputStreamPosition;
             imageInput.seek(inputStreamPosition);
         }
         catch (EOFException e) {
-            //Retry byte by byte
+            // Retry byte by byte
             streamPosition = inputStreamPosition - 8;
             bitOffset = 64;
             refillBuffer();
         }
 
     }
 
-    //Left for backwards compatibility / Compatibility with ImageInputStream interface
+    // Left for backwards compatibility / Compatibility with ImageInputStream interface
     public int readBit() throws IOException {
         return (int) readBits(1);
     }

imageio/imageio-webp/src/main/java/com/twelvemonkeys/imageio/plugins/webp/WebPImageReader.java

@@ -96,7 +96,9 @@ protected void resetMembers() {
     public void setInput(Object input, boolean seekForwardOnly, boolean ignoreMetadata) {
         super.setInput(input, seekForwardOnly, ignoreMetadata);
 
-        lsbBitReader = new LSBBitReader(imageInput);
+        if (imageInput != null) {
+            lsbBitReader = new LSBBitReader(imageInput);
+        }
     }
 
     private void readHeader(int imageIndex) throws IOException {
@@ -272,19 +274,19 @@ private void readHeader() throws IOException {
                 }
 
                 // RsV|I|L|E|X|A|R
-                int reserved = (int) imageInput.readBits(2);
+                int reserved = lsbBitReader.readBit();
                 if (reserved != 0) {
                     // Spec says SHOULD be 0
                     throw new IIOException(String.format("Unexpected 'VP8X' chunk reserved value, expected 0: %d", reserved));
                 }
 
-                header.containsICCP = imageInput.readBit() == 1;
-                header.containsALPH = imageInput.readBit() == 1; // L -> aLpha
-                header.containsEXIF = imageInput.readBit() == 1;
-                header.containsXMP_ = imageInput.readBit() == 1;
-                header.containsANIM = imageInput.readBit() == 1; // A -> Anim
+                header.containsANIM = lsbBitReader.readBit() == 1; // A -> Anim
+                header.containsXMP_ = lsbBitReader.readBit() == 1;
+                header.containsEXIF = lsbBitReader.readBit() == 1;
+                header.containsALPH = lsbBitReader.readBit() == 1; // L -> aLpha
+                header.containsICCP = lsbBitReader.readBit() == 1;
 
-                reserved = (int) imageInput.readBits(25); // 1 + 24 bits reserved
+                reserved = (int) lsbBitReader.readBits(26); // 2 + 24 bits reserved
                 if (reserved != 0) {
                     // Spec says SHOULD be 0
                     throw new IIOException(String.format("Unexpected 'VP8X' chunk reserved value, expected 0: %d", reserved));
@@ -509,15 +511,15 @@ private void readVP8Extended(BufferedImage destination, ImageReadParam param, lo
     }
 
     private void readAlpha(BufferedImage destination, ImageReadParam param, final int width, final int height) throws IOException {
-        int reserved = (int) imageInput.readBits(2);
+        int reserved = (int) lsbBitReader.readBits(2);
         if (reserved != 0) {
             // Spec says SHOULD be 0
             processWarningOccurred(String.format("Unexpected 'ALPH' chunk reserved value, expected 0: %d", reserved));
         }
 
-        int preProcessing = (int) imageInput.readBits(2);
-        int filtering = (int) imageInput.readBits(2);
-        int compression = (int) imageInput.readBits(2);
+        int preProcessing = (int) lsbBitReader.readBits(2);
+        int filtering = (int) lsbBitReader.readBits(2);
+        int compression = (int) lsbBitReader.readBits(2);
 
         if (DEBUG) {
             System.out.println("preProcessing: " + preProcessing);

imageio/imageio-webp/src/main/java/com/twelvemonkeys/imageio/plugins/webp/lossless/ColorIndexingTransform.java

@@ -55,7 +55,7 @@ public void applyInverse(WritableRaster raster) {
         byte[] rgba = new byte[4];
 
         for (int y = 0; y < height; y++) {
-            //Reversed so no used elements are overridden (in case of packing)
+            // Reversed so no used elements are overridden (in case of packing)
             for (int x = width - 1; x >= 0; x--) {
 
                 int componentSize = 8 >> bits;
@@ -67,7 +67,7 @@ public void applyInverse(WritableRaster raster) {
 
                 int index = sample >> componentOffset & ((1 << componentSize) - 1);
 
-                //Arraycopy for 4 elements might not be beneficial
+                // Arraycopy for 4 elements might not be beneficial
                 System.arraycopy(colorTable, index * 4, rgba, 0, 4);
                 raster.setDataElements(x, y, rgba);
 

imageio/imageio-webp/src/main/java/com/twelvemonkeys/imageio/plugins/webp/lossless/HuffmanInfo.java

@@ -37,7 +37,7 @@
  * @author Simon Kammermeier
  */
 final class HuffmanInfo {
-    public Raster huffmanMetaCodes; //Raster allows intuitive lookup by x and y
+    public Raster huffmanMetaCodes; // Raster allows intuitive lookup by x and y
 
     public int metaCodeBits;